40°F outside, 80°F under the plastic
|
Last week I swapped out my worn-out frost covers for fresh ones, and it reminded me of the question I get more than any other this time of year: fabric or plastic? I know, plastic sounds like the obvious winner. It's clear, it traps more heat, and it looks like a little greenhouse. But warmer isn't always better for cool-season crops. On a sunny winter day when it's only 40°F outside, a plastic-covered tunnel can easily climb to 80°F inside. Your kale and spinach take that as a cue to drop the sugars they've built up to survive freezing (their own natural antifreeze). Then the sun goes down. (This is why I vent my plastic tunnel anytime it creeps toward 60°F inside.) Fabric breathes, so it vents itself. It lets winter rain soak through to thirsty roots, and it doubles as shade cloth when summer turns scorching. That's why most of my beds sit under medium-weight frost cloth from now until my last expected frost in June (which is kinda ridiculous, but that's Central Oregon for ya). But plastic still earns a spot in my garden for a few jobs: mature lettuce and chard that would go limp under fabric, winter sowing for a head start on spring, and shedding snow faster after a storm. So the right cover comes down to how you garden: how often you can get out there, how much snow you get, and what you're hoping to harvest. Seasonal tipsP.S. If you only read one section, make it #3 in the row cover guide. It explains why baby Asian greens shrug off a hard freeze under fabric while the full-grown ones turn to mush (and how to time your sowings around it). P.P.S. Row covers are all about timing: pull the fabric down before a freeze, vent the plastic when a sunny day climbs past 40°F, and brush off the snow after a storm. ​Bloomcast, my weather dashboard built for gardeners, alerts you to frosts, freezes, and incoming storms for your location, with hourly highs and lows so you know when to vent. It's included with Garden Betty Plus. |
Garden Betty
For people who want to grow more food with less work. 🌱 This is my weekly newsletter loved by 38,000+ subscribers—here's what one of them had to say: "These are not the regular run-of-the-mill garden-based emails. You actually touch on more unusual tidbits that encourage me to keep growing and learning."